JP2591111Y2 - Variable sound field playback device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable sound field reproducing apparatus for processing a music signal or the like to variably reproduce an arbitrary sound field, and more particularly to an improvement of a variable sound field reproducing apparatus suitable for use in a vehicle.

[0002]

2. Description of the Related Art Generally, a sound field is composed of a direct sound reaching a listener first and a group of reflected sounds arriving later than the direct sound. Therefore, in order to reproduce the sound field, it is necessary to accurately reproduce the direct sound and the reflected sound group.

Conventionally, there is a device as shown in FIGS. 5 and 6 as a device for variably reproducing such a sound field.

In the variable sound field reproducing apparatus shown in FIG. 5, an input signal a such as a music signal is branched, and one of the branched signals is directly input to the adder 10 as a direct sound signal. And a plurality of sets of delay circuits 7 and coefficient units 9 provided in parallel with the other branch signals.
To generate the reflected sound signals one by one independently, and input these reflected sound signals to the adder 10 to synthesize them, thereby reproducing the sound field as shown in FIG. ing.

When the sound field is changed, the time interval and level of each reflected sound signal are changed by changing the delay time of the delay circuit 7 and the coefficient value of the coefficient unit 9. (A) and (b) of FIG. 11 show how the sound field is changed by the present apparatus.

On the other hand, the variable sound field reproducing apparatus shown in FIG. 6 divides a reflected sound group into an initial reflected sound group (reflected sound reaching up to 50 ms with respect to a direct sound) and a reverberant sound, and It reproduces a sound field composed of groups and reverberation.

That is, one of the branch signals of the input signal a is used as a direct sound signal, and the other branch signals are used as an initial reflected sound generator 23 for generating an initial reflected sound group and a reverberation for generating a reverberant sound signal. 10 is input to the sound generation unit 24, and these output signals are input to the adder 10 to be synthesized.
A sound field as shown in (b) is reproduced.

The initial reflected sound generating section 23 is composed of a plurality of sets of delay circuits 7 and coefficient units 9 provided in parallel substantially in the same manner as the apparatus of FIG. 5 described above. 6 and a comb filter 25 having a feedback loop (feedback unit) as shown in FIG.

To change the sound field, the delay time of the delay circuit 7 of the initial reflected sound generator 23 and the coefficient value of the coefficient unit 9 are changed to change the delay time and level of the initial reflected sound signal. Filter 2 constituting the reverberation generator 24
5, the reverberation time of the reverberation sound signal (the time until the reverberation sound signal is attenuated by 60 dB with respect to the level of the direct sound signal) is changed by changing the coefficient value of the coefficient unit 9 and the delay time of the delay circuit 7. (A) and (b) of FIG. 12 show how a sound field is changed by the present apparatus.

[0010] As described above, the reverberation sound generation unit 24 has
In general, a circuit structure as shown in FIG. However, the reflected sound (especially the reverberant sound) has a property that the high-frequency component level is attenuated as the reflection is repeated (the delay time becomes larger than the direct sound), and the circuit structure shown in FIG. The reverberation generator 24 cannot satisfy such characteristics of reverberation.

Therefore, in consideration of such characteristics of the reverberation sound, the reverberation sound generation unit 24 has a circuit structure as shown in FIGS. 8 and 9, and attenuates the high-frequency component level of the reverberation sound signal in a pseudo manner. A device has been devised.

That is, in the reverberation generator 24 shown in FIG. 8, a BPF (band-pass filter) 26 is provided downstream of the all-pass filter 13 so that the high-frequency component level of the reverberation signal is reduced at once. In the reverberation generation unit 24, LPF (low-pass filter) 27, BPF 28, HPF (high-pass filter) 2
9, the reverberation time of the reverberation signal is set by dividing the band of the input signal into low, middle, and high bands and changing the coefficient value of the feedback section of the comb filter 25. The high frequency component level of the sound signal is attenuated.

[0013]

However, the conventional variable sound field reproducing apparatus shown in FIGS. 5 and 6 can reproduce only one kind of sound field.

That is, the apparatus shown in FIG. 5 can reproduce only the sound field shown in FIG. 10A, and the change in the sound field can be changed as shown in FIGS. 11A and 11B. Only within range. Also, the apparatus shown in FIG. 6 can reproduce only the sound field shown in FIG. 10B, and as shown in FIGS. 12A and 12B, the sound field changes within the range of the sound field of the kind. I can only do it. Therefore, the conventional variable sound field reproduction device cannot reproduce each type of sound field with one device, and the variable range of the sound field is narrow.

In the variable sound field reproducing apparatus shown in FIG. 6, the reverberant sound generator 2 having a circuit structure as shown in FIGS.
In some cases, the reverberation signal generator 24 shown in FIG. 8 uses the BPF 26 to drop the high-frequency component level of the reverberation signal, so that the high-frequency level of the entire reverberation signal drops. As a result, the sense of spread of the sound received in the sense of hearing disappears. Further, the reverberation generation unit 24 shown in FIG.
In this case, a reverberation time gap is formed at the boundary between the divided bands, and a very unnatural reverberation sound is generated.

Further, since the interior of the vehicle is spatially narrow and has many opposing surfaces, when the above-described conventional sound field variable reproducing apparatus is used in a vehicle and used in the interior of the vehicle, a standing wave is generated in a low frequency range. Then, it becomes muffled sound.

By the way, in recent years, it is general to realize the above-mentioned conventional sound field variable reproducing apparatus using a DSP (Digital Signal Processor).

In this case, two types of sound field changing methods are employed. In the first method, a program (algorithm) corresponding to the apparatus shown in FIGS. 5 and 6 is provided, and by changing this program, the program shown in FIG.
In the second method, only the coefficient corresponding to the delay time of the delay circuit 7 or the coefficient value of the coefficient unit 9 is changed without changing the program.

However, in the first method, since the two types of sound fields shown in FIGS. 10A and 10B can be selected, the variable range of the sound field can be increased. There is a disadvantage that the sound is interrupted when the sound field is switched (when the program is changed). In the second method, the sound field is not switched so that the sound field can be changed without sound interruption. Therefore, there is a disadvantage that the variable range of the sound field is narrow.

The present invention has been made to solve the above-mentioned conventional problems, and can reproduce a natural sound field, has a wide variable range of the sound field, and has no sound interruption when switching the sound field. An object of the present invention is to provide a variable sound field reproduction device.

[0021]

The variable sound field reproducing apparatus of the present invention comprises an initial reflected sound generating means (3), a reverberant sound generating means (5), a switching means (12), and a reflected sound generating means (1).
6) A variable sound field reproduction device comprising a control means (17) and a synthesis means (2), wherein the initial reflected sound generation means (3) comprises:
The input signal is delayed for a predetermined time and changed to a predetermined level to generate an initial reflected sound signal, and a reverberation sound generating means (5)
Comprises a plurality of feedback means (6) and an adding means (10). The feedback means (6) performs a delay process on the initial reflected sound signal with a delay time different from that of the initial reflected sound generating means (3);
Variable processing and feedback processing to a predetermined level different from the initial reflected sound generating means (3) are performed and output, and the adding means (10)
Generates a reverberation signal by adding the output of the feedback means (6), and the switching means (12) outputs the reverberation signal to the first output terminal or the second output terminal under the control of the control section (17). The reflected sound generation means (16) delays the reverberation sound signal from the second output end for a predetermined time to generate a reflected sound signal, and the control means (17) controls the switching means (12). And the variable level of the delay signal of the feedback means (6) in response to the switching, and the synthesizing means (2) outputs the input signal, the initial reflected sound signal and the first output terminal. Or a reverberation sound signal or a reflection sound signal.

Further, the variable sound field reproducing device according to the second aspect is characterized in that a low-pass filter (8) is provided in the feedback section (6) of the reverberation sound generating means (5).

Further, the variable sound field reproducing apparatus according to the third aspect is characterized in that a high-pass filter (15) is provided between the switching means (12) and the synthesizing means (2).

[0024]

According to the first aspect of the present invention, an initial reflected sound signal is generated from the reproduced sound signal by the initial reflected sound generating means. If the switching means is operated by variably setting the delay time and the level by the control means, the processing of either the reverberation sound generation means or the reflection sound generation means is performed, and the processing of the reverberation sound generation means is performed. A signal or a reflected sound signal is generated by processing of the reflected sound generating means. The direct sound signal as the reproduced sound signal, the initial reflected sound signal, and the reverberant sound signal or the reflected sound signal are synthesized by the synthesizing means, and the sound field of each mode is reproduced.

Further, according to the sound field variable reproducing device of the second aspect, the reverberant sound signal whose high-frequency component level gradually decreases is generated by the low-pass filter.

Further, according to the sound field variable reproduction device of the third aspect, a reverberation signal from which low-frequency components have been removed by a high-pass filter is generated.

[0027]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration of a variable sound field reproducing apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a branch point at which an input signal a is branched. One branch signal is directly input to the synthesizer 2 as a direct sound signal a, and the other branch signal a is input to the initial reflected sound generator 3. It has become so.

The initial reflected sound generation unit 3 has a circuit structure in which a plurality of sets of delay circuits 7 and coefficient units 9 are connected in parallel, similarly to the initial reflected sound generation unit 23 shown in FIG. The branch signal a input to the initial reflected sound generation unit 3 is shown in FIG.
As in the case of the initial reflected sound symbol shown in (b), it is output as a discrete signal at a predetermined level and a predetermined delay time interval.

The signal b is branched at the branch point 4 such that one branch signal b is directly input to the synthesizing section 2 as an initial reflected sound signal as it is, and the other branch point signal b is input to the comb filter 5. Has become. The comb filter 5 includes two comb filter circuits 6 and 6 connected in parallel, and an adder 10 for adding the output signal c from the comb filter circuits 6 and 6.

Each comb filter circuit 6 includes a delay circuit 7 and cutoff frequencies 1 to 1 corresponding to the first filter of the present invention.
3 KHz LPF (low-pass filter) 8 and coefficient unit 9
And the adder 10 at the preceding stage. As a result, the branch signal b input to each comb filter circuit 6 is output as a signal c having an impulse response c (t) represented by the following equation (1), as shown in FIG. Where δ (t) is a delta function, t is time,
τ is the delay time of the delay circuit 7, and g is the coefficient value of the coefficient 9.

C (t) = δ (t−τ) + g · δ (t−2τ) + g ² · δ (t−3τ) + g ³ · δ (t−4τ) + (1) Since the LPF 8 is provided in the feedback section, the branch signal b input to the comb filter circuit 6 repeats feedback, so that the signal c whose level of the high-frequency component gradually decreases is output from the comb filter circuit.

Reference numeral 12 denotes a multiplexer for connecting the output side of the comb filter 5 to the all-pass filter 13 or the reflected sound generator 16 . All-pass filter 13
Is connected to the comb filter 5 to form the reverberation sound generator 14, and has the same circuit structure as the all-pass filter shown in FIG. As a result, the output from the comb filter 5 is output to the all-pass filter 1 through the multiplexer.
3 is output as a reverberation signal d having an impulse response d (t) represented by the following equation (2) as shown in FIG.

D (t) = − g · δ (t) + (1−g ² ) ｛δ (t−τ) + g · δ (t−2τ) +... (2) This all-pass filter 13 The second part of the present invention
A high pass filter (HPF) 15 having a cutoff frequency of about 300 Hz corresponding to the above filter is provided. The reverberation signal d output from the all-pass filter 13 is:
The low-pass component level is cut off by the HPF 15 and output to the synthesizing unit 2.

On the other hand, the reflected sound generator 16 outputs the signal c ′ input from the comb filter 5 via the multiplexer 12.
To generate a reflected sound signal e slightly delayed from the initial reflected sound signal b generated by the initial reflected sound generating section 3 based on the above, and has a circuit structure substantially similar to that of the initial reflected sound generating section 3. .

A control unit 17 controls switching of the multiplexer 12 and sets the delay time of the delay circuit 7 of each unit and the coefficient value of the coefficient unit 9, and is formed by a microcomputer. Note that the control unit 17 controls the comb filter 5
When the multiplexer 12 is controlled so as to connect with the reflection sound generation unit 16, the coefficient value of the coefficient unit 9 of the comb filter 5 is set to zero at the same time. 18
Is a sound field changeover switch that issues a changeover control command of the control unit 17.

Next, the operation of this embodiment will be described.

When an input signal a such as a music signal is input,
The direct sound signal a having the same level as the input signal a is branched into two at the branch point 1, and is input to the synthesizing unit 2, and another branched signal a is input to the initial reflected sound generating unit 3.

The branch signal a input to the initial reflected sound generation unit 3 is delayed and leveled by a plurality of sets of delay circuits 7 and coefficient units 9, converted into a discrete signal b at a predetermined time interval, and output. You. The signal b is branched at the branch point 4, and one branch signal is input to the synthesizing unit 2 as an initial reflected sound signal b delayed from the direct sound signal a, and the other branch signal b is input to the comb filter.

Here, when the multiplexer 12 connects the comb filter 5 and the all-pass filter 13 to form the reverberation sound generator 14, the reverberation sound generator 14
The reverberation signal d is generated and output. That is,
In each comb filter circuit 6 of the comb filter 5, a signal c shown in FIG. 2 is generated for each impulse of the branch signal b, added by the adder 10 at the subsequent stage, input to the all-pass filter 13 as a signal c ′, and output to the all-pass filter 13. FIG. 3 shows each impulse of the input signal c ′ in FIG.
Is generated.

Further, the branch signal b input to each comb filter circuit 6 is cut off the high-frequency component level by the LPF 8 at the time of feedback and is attenuated by the coefficient unit 9, so that the signal c 'output from the comb filter 5 is It becomes a signal in which the high-frequency component level decreases as time elapses. As a result, the reverberation signal d output from the all-pass filter 13 becomes a natural reverberation signal in which the high-frequency component level gradually decreases.

The low-frequency component level of the reverberation signal d is cut by the HPF 15 and output to the synthesizing unit 2. Therefore, the direct sound signal a and the early reflected sound signal b
, And then the reverberation signal d whose high-frequency component level is gradually attenuated and whose low-frequency component level is removed is input. As a result, the synthesizer 2 synthesizes the sound field including the natural reverberation shown in FIG.

Further, the sound field changeover switch 18 is changed over,
The control unit 17 controls switching of the multiplexer 12,
When the comb filter 5 and the reflected sound generator 16 are connected, the controller 17 sets the coefficient value of the coefficient unit 9 of the comb filter 5 to zero. As a result, the feedback section of the comb filter 5 is closed, and only the delay circuit 7 of the comb filter 5 functions. Accordingly, a signal c ′ that is delayed from the initial reflected sound signal b is output from the comb filter 5 and is input to the reflected sound generating unit 16.

The signal c ′ input to the reflected sound generator 16 is
The signals are delayed and leveled by a plurality of sets of delay circuits 7 and coefficient units 9, converted into discrete reflected sound signals e at predetermined time intervals, and output to the synthesis unit 2. Accordingly, the direct sound signal a, the initial reflected sound signal b, and the discrete reflected sound signal e slightly delayed from the initial reflected sound signal b are input to the synthesizing unit 2. The sound field shown in a) is synthesized.

As described above, the sound field variable reproducing apparatus of this embodiment can reproduce any of the sound fields shown in FIGS. 10A and 10B, and furthermore, the sound field switch 18
, The sound field reproduction processing method is switched, so that there is no sound interruption when switching the sound field mode.

The delay time of the delay circuit 7 and the coefficient unit 9
By changing and setting the coefficient value of the sound field, a sound field of a hall or a church, a sound field of a stadium, a sound field of a disco, or the like as shown in FIGS. 4A to 4C can be reproduced. Wide range.

Further, the reverberation sound signal d is not directly generated from the sound signal a, but is generated from a plurality of discrete initial reflection sound signals b generated through the initial reflection sound generation unit 3. Therefore, the reverberation density (the number of reverberation sounds per unit time) can be increased.

Further, the LPF 8 is connected to the feedback section of the comb filter 5.
Is provided so that the high-frequency component level of the reverberation sound signal d attenuates with time, so that a natural reverberation sound can be reproduced. Moreover, since the low-frequency component level of the reverberation signal d is removed by the HPF 15, even when this device is used in a vehicle and used in a vehicle cabin, a standing wave is not generated, and a clean sound without muffled sound is generated. The place can be regenerated.

[0049]

According to the sound field variable reproducing apparatus of the present invention, the synthesizing section synthesizes the direct control signal, the initial reflected sound signal, and the reverberant sound signal or the reflected sound signal and outputs the synthesized signal. Therefore, even if the reverberation sound signal and the reflected sound signal are switched, there is no sound interruption because only the direct signal sound and the initial reflected signal sound are always output from the synthesis unit. In addition, since the reverberation sound generation device can generate a reverberation sound signal in which the high-frequency component level gradually decreases, natural reverberation sound can be reproduced. further,
Since the reverberation sound signal is generated not from the direct control signal as the reproduction sound signal but from the early reflection sound, the reverberation density can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an output signal of a comb filter.

FIG. 3 is a diagram showing an output signal of an all-pass filter.

4A and 4B are diagrams showing sound fields, wherein FIG. 4A shows a sound field of a hall or a church, FIG. 4B shows a sound field of a stadium, and FIG. 4C shows a sound field of a disco.

FIG. 5 is a block diagram showing a conventional sound field variable reproduction device.

FIG. 6 is a block diagram showing another example of the conventional variable sound field reproduction device.

FIG. 7 is a block diagram illustrating a reverberation sound generation unit of the variable sound field reproduction device of FIG. 6;

FIG. 8 is a block diagram showing a first modification of the reverberation sound generator of the variable sound field reproduction device of FIG. 6;

FIG. 9 is a block diagram showing a second modification of the reverberation sound generator of the variable sound field reproduction device of FIG. 6;

FIG. 10 is a diagram showing various sound fields, and FIG.
FIG. 10 is a diagram illustrating a sound field reproduced by the variable sound field reproduction device of FIG. 5, and FIG. 10B is a diagram illustrating a sound field reproduced by the variable sound field reproduction device of FIG. 6.

11 is a diagram showing a variable state of a sound field by the variable sound field reproduction device of FIG. 5;

12 is a diagram showing a variable state of a sound field by the variable sound field reproduction device of FIG. 6;

[Explanation of symbols]

 2 Synthesizing unit (synthesizing unit) a Direct signal 3 Initial reflected sound generating unit (initial reflected sound generating unit) b Initial reflected sound signal 5 Com filter 7 Delay circuit 8 Low-pass filter (first filter) 9 Coefficient unit 12 Multiplexer (Switching unit) 13 all-pass filter 14 reverberant sound generator (reverberant sound generator) 15 high-pass filter (second filter) d reverberant sound signal 16 reflected sound generator (reflected sound generator) e reflected sound signal 17 controller (controller) 18 Sound field switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G10K 15/12 G10K 15/00

Claims (3)

(57) [Scope of request for utility model registration] 1. An initial reflected sound generating means (3), a reverberant sound generating means (5), a switching means (12), and a reflected sound generating means (1).
6) A sound field variable reproducing apparatus comprising a control means (17) and a synthesizing means (2), wherein the initial reflected sound generating means (3) delays an input signal for a predetermined time and changes the input signal to a predetermined level to initialize the input signal. A reverberation sound generating means (5) comprises a plurality of feedback means (6) and an adding means (10). The feedback means (6) generates an initial reflected sound signal for the initial reflected sound signal. A delay processing with a delay time different from that of the means (3), a variable processing to a predetermined level different from that of the initial reflected sound generation means (3), a feedback processing, and an output. The adding means (10) is a feedback means ( The output of step 6) is added to generate a reverberation signal, and the switching means (12) is controlled by the control section (17).
The reverberation signal is switched to the first output terminal or the second output terminal and output, and the reflected sound generation means (16) delays the reverberation signal from the second output terminal for a predetermined time to generate a reflected sound signal The control means (17) controls the switching operation of the switching means (12) and, in response to the switching, returns the feedback means (6).
Wherein the synthesizing means (2) synthesizes the input signal, the initial reflected sound signal, and the reverberant sound signal or the reflected sound signal from the first output terminal. Variable playback device. 2. The feedback section (6) of the reverberation sound generating means (5).
The variable sound field reproducing device according to claim 1, wherein the device has a low-pass filter (8). 3. The variable sound field reproduction device according to claim 1, wherein a high-pass filter is provided between the switching means and the synthesizing means.